<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>多个子元素居中显示</title>
    <style>
        .box1 {
            width: 1000px;
            height: 300px;
            background-color: red;
        }
        .box2 {
            width: 600px;
            height: 200px;
            position: relative;
            top: 50px;
            margin-left: auto;
            margin-right: auto;
        }
        .box2_1 {
            width: 200px;
            height: 200px;
            background-color: yellow;
        }
        .box2_2 {
            width: 200px;
            height: 200px;
            background-color: #bfa;
            position: relative;
            left: 200px;
            top: -200px;
        }
        .box2_3 {
            width: 200px;
            height: 200px;
            background-color: blue;
            position: relative;
            left: 400px;
            top: -400px;
        }
    </style>
</head>
<body>
    <div class="box1">
        <div class="box2">
            <div class="box2_1">1</div>
            <div class="box2_2">2</div>
            <div class="box2_3">3</div>
        </div>
    </div>
</body>
</html>